A BT (back-illuminated thinning)-CCD is known as a back-illuminated solid-state image pickup device with which a light incident surface side of a substrate is thinned. According to Non-Patent Literature 1, interference (etaloning) occurs between light to be detected made incident on the BT-CCD and light resulting from the incident light to be detected reflecting from a detection side surface of the BT-CCD, thereby affecting detection characteristics in a near-infrared range. In the literature, to suppress the etaloning, a photosensitive region is increased in thickness and further, an anti-reflection film is provided on the photosensitive region.